A little help with drops on 338 rum

[D.Camilleri]

OK, I am trying to learn to stretch my ranges out and I am stuck at 700 yards with a question. I just started using 300 gr bergers and they seem to be doing great. I went to the range today and made up a new drop chart from vortex site. My chono showed 2858, my elevation is 4200, temp today was 80. I dialed the scope dead on at 100 and then dialed 53 clicks for my 700 yard shot. Two shots, both hit high. One shot about 10 inches above POA and the other about 15 inches above. I was also several inches left. I moved one click right and down two clicks. My next three shots hit about 8 inches below POA. I came up one click and fired two more and I was still about 7 inches low. I dialed up one more click, same as where I started and was 6 inches below POA. The groups kept getting better the more I shot. The barrel was super clean when I started with 4 shots at 100, so the first two shots at 700 were no. 5 and 6. The barrel was warm, but not hot. I am thinking of shooting again in the morning without cleaning the barrel and see where the shots place. Am I missing anything?

I also dialed back 11 clicks according to my drop chart and center punched a gong at 600 yards on my last shot. I want to keep stretching the range, but I need to find out why my POA is changing. Any thoughts?

 

[D.ID]

Check your rings and BASE. 10" high, 15" high left then a couple clicks dropped 8" low......... sounds like a loose base. double check your zero first thing. Something in the mechanics is moving to create that much inconsistency. When I had similar problems it kept leading back to the scope base. Now I bond those suckers to the action.

 

[angus-5024]

your barrel is deffinatley a "dirty girl". My .338 RUM starts to get good after 8 shots, but really shines around 10 down the tube.

Like D.I.D has already said, check the mounts.

one other thing is that your scope could have poor tracking... Have you done a box test? I think ive heard you say that its a Sightron, so I doubt that its the problem, but every once in awhile one slips through.

 

[bruce_ventura]

I agree with D.ID and angus. I would check the scope installation, starting with the rings. Does the base mate to the receiver well? Did you lap the rings? Are all the screws properly torqued?

I think you should check your groups at 100 yds. Start with a clean barrel. Fire two sighters. Then fire three groups of five shots each for score. Do successive groups get smaller?

Also, your scope has 1/2 moa clicks? What model is it?

Have fun.

 

[D.Camilleri]

The scope is a Sightron SIII 8-32 x56, the rings are burris extra high dual dovetail with inserts. The repeatability of the scope is good. It tracks back to the same place every time. It seems that maybe I have been guilty of cleaning too often, usually after around 10 shots. It seems that the accuracy is getting better after 8 + rounds and then the POI is settling down. I wanted to go out and test this theory today, but the wind was more than I wanted to test this theory. My theory is that the barrel starts grouping tighter with more shots down the tube. The barrel is a broughton 5C and it cleans very easily. I want to test POI compared to the last shots I took yesterday to see if a cold shot with a dirty bore will duplicate where the rounds were hitting at the end of my session yesterday. At the end of my shooting session yesterday, I was grouping under 4 inches and when I made adjustments to the scope, the bullet was moving like it should. More testing and I will report back.

 

[D.Camilleri]

I went to the range this morning before work and popped off two shots @ 700, my target from the other day was still intact. I had about a 5 mph wind from the west, so I held at the west edge of my 8x11 target. First shot from a cold bore, 2 inches high from point of aim. Next shot, 12 inches high, 6 inches west from point of aim. Not much time, so I took one shot at 100 yards to check zero elevation perfect, 2 inches west from point of aim. When I shot at 700, I dialed 54 clicks up. My first two shots the other day were dialed 53 clicks up and they were about 4 inches higher than my shots today. The other day temps were about 75+, this morning was about 40 with a cold front coming in.

So the big question is now why did my point of impact change lower the other day as the barrel warmed up? I haven't cleaned the barrel and I am up to about 18 rounds since cleaning. I am wondering if lack of clearance in my barrel channel could be a problem. When I free floated this new B&C alaskan stock, I can barely get a piece of paper in between the barrel and the stock. Should I remove some more material? I will try the recommendation of several 5 shot groups at 100 to see what my loads are doing. I haven't adjusted powder charges or oal at all since these shot so good first time out. My oal is max for my magazine and powder charge is 91 gr H-1000 velocity showed 2850+- with SD of under 20

 

[angus-5024]

I would deffinatley remove a bit more material. My rule of thumb is thick computer paper folded twice (four thick). are you shooting from a bench or bi-pod? do you load your bi-pod for the shot (can cause flex on the fore-end)?

Have you chorographed your load? You can shoot good groups at 100 yards but if you have big extreme spread, or even small ES itll show at 700.

I might be saying what you already know, but gotta sort through the variables.

 

[D.ID]

Agree with angus about removing more material around the barrel. Personally I want daylight shining threw between the stock and barrel but thats just me. h1000 can usually shrug off 30 degrees with little notice, my cold bore is always higher than subsequent shots but not by much. Unless you were just having an off day behind the trigger: the extremes you experienced the other day will resurface at the least opportune time. I don't expect 18 rounds fired is enough to have so much effect as I frequently shoot 2-3 times that much between cleanings and I shoot a factory savage barrel. All that being said the ten inch jump from the first to second shot screams mechanical slop somewhere. I am assuming the rifle is capable of far better accuracy than a 12"@700.....a couple thousands of slip may not show up at a hundred yards but will be vary pronounced at seven hundred, Try grouping at 700 to get a better picture. !!!!!!!!!!!!OH SH#@$!!!! hold the phone...........I just realized your using burris signature rings with inserts on a 338 rum. I used them on my edge until I went threw what your going threw..... over and over again. ........Change rings..........I know the whole shooting community is now going to rush to burris's defense but get some good tactical rings and move the burris signatures to win mag or smaller caliber. I tried everything under the sun and they could not hold the heavy scope on the big rifle. Subtle movement only under recoil without ring marks had me chasing ghosts for months.

 

[D.Camilleri]

Agree with angus about removing more material around the barrel. Personally I want daylight shining threw between the stock and barrel but thats just me. h1000 can usually shrug off 30 degrees with little notice, my cold bore is always higher than subsequent shots but not by much. Unless you were just having an off day behind the trigger: the extremes you experienced the other day will resurface at the least opportune time. I don't expect 18 rounds fired is enough to have so much effect as I frequently shoot 2-3 times that much between cleanings and I shoot a factory savage barrel. All that being said the ten inch jump from the first to second shot screams mechanical slop somewhere. I am assuming the rifle is capable of far better accuracy than a 12"@700.....a couple thousands of slip may not show up at a hundred yards but will be vary pronounced at seven hundred, Try grouping at 700 to get a better picture. !!!!!!!!!!!!OH SH#@$!!!! hold the phone...........I just realized your using burris signature rings with inserts on a 338 rum. I used them on my edge until I went threw what your going threw..... over and over again. ........Change rings..........I know the whole shooting community is now going to rush to burris's defense but get some good tactical rings and move the burris signatures to win mag or smaller caliber. I tried everything under the sun and they could not hold the heavy scope on the big rifle. Subtle movement only under recoil without ring marks had me chasing ghosts for months.

Hmmm my rings are suspect. This is good to know, because I have been chasing this with all of my loads at extended range and the gun shoots very well. So the next question is what rings should I go with? I currently have extra high to clear the 56 mm bell. Do I need to take the plunge and go with a picany rail and tactical rings or can I simply go back with Leupold dual dovetail 30 mm? Thanks for the insight.

 

[D.ID]

There are allot of good ones out there but I would go to an extra wide tactical ring or a one piece base with three rings. I was plagued with problems when I switched from a 10x40 up to the big scope. My rifle does not kick hardly at all to the shoulder but the heavy weight scope combined with the pulse of this thing gave me some grief. I went into overkill mode remedying it after having spent considerable time and ammo searching for the weak link. I am still thrilled everytime I shoot it that I do not have to worry about it ever again.

 

[D.Camilleri]

D.ID

What brand of rail and rings did you go with? Are the Burris tactical rings any good? Should I go with a 20 minute rail? Do I need a specific rail for a lh action? Thanks

 

[dieseldoc]

Go with Nightforece or Near bases and rings and your problems will be hind you.

Charliegun)

 

[D.ID]

I would suggest normal people just get a quality set of tac rings or one piece base and three good rings............It is entirely possible I do not qualify as normal so what I did........ I am well aware no sane person would do what I have done...... I was very frustrated at the time and am completely ecstatic with the end result so that being said......I got in my parts bin and went crazy..... glad I did. I already had a weaver 20 moa tac base (minus forward extended lugs) bedded onto the receiver, I used some devcon with kiwi release agent to take up any space between the rail and rings, basically bedding rings to base. I took 2 pair (yes 2 pair=4) weaver six hole tac rings. Front and back rings where lapped about 80%. The bottom half of the two rings in the middle where skimmed with my dremel to make room for devcon.....................the scope was installed without release agent and without caps on the two middle rings. after curing I installed the cap on the forward interior ring and a mounting solutions clamp-on anti cant ring (top and bottom) were used to make the top of the rear interior ring. I warned you I went into overkill mode but the end result is both beautiful and 100% solid for snowmobiling, four wheeling and a couple hundred rounds since. There is simply no doubt anywhere in that rifle system. Again, this is me and "normal" people probably do not need to do this. I had developed trust issues and needed extreme measures. Final solutions that I could bet the world on....................D

 

[MachV]

The 30mm Ruger and Leupold rings have failed on my 338Edge. With the limited ring options for the Ruger my solution has been to drill out the little screw they use to mount the rings to the reciever and put in a bigger one.
About left the Edge out in the field last fall on the last day of goat season= Missed three goats by a LOT. Gave the Edge a time out in the safe for a couple months When I brought it back out I was going to replace the scope to see if that was the problem= Nope the screw was broke off the back ring, had another ring sitting here so I just replace the ring with another one that lasted a total of 24 rounds before it too broke.
Hopeing the bigger screws,lapping and bedding the rings in hold as this thing is kinda spendy to be throwing ammo down range at random!
Overkill is underatedlightbulb